Short-Pulse Intrinsic Tunneling Spectroscopy in Bi2Sr2CaCu2O8+δ under Suppressed Self Heating

Short-pulse tunneling spectroscopy on a time scale of 300 ns has been conducted using intrinsic Josephson junctions naturally built in the crystal structure of a slightly underdoped Bi2Sr2CaCu2O8+δ (Bi2212) by fabricating a very small and thin mesa of 6 nm in thickness and less than 5 µm in square width. The results are characterized by a pronounced superconducting peak at 79 meV accompanied by a broad pseudgap at a much higher energy of 125 meV, indicating discrete nature of both energy structures. The temperature rise due to self-heating in a small mesa is numerically calculated based on temperature-dependent thermal conductivity and specific heat for each constituent material. It is found that the temperature rise is less than 2 K for the present experiment, which reinforces that the tunneling spectra obtained represent the genuine superconducting properties of Bi2212.